A known rotary electrical apparatus includes a housing in which a stator and a rotor are accommodated and in which oil is stored. Such rotary electrical apparatus is disclosed in JP2008-286247A (hereinafter referred to as Reference 1). In Reference 1, it is stated that, in a case where an amount of oil stored in the housing increases, a stirring resistance of the rotor increases. The increase of stirring resistance leads to a decrease in efficiency of the rotary electrical apparatus. On the other hand, in a case where the amount of oil stored in the housing decreases, a function of oil may not be sufficiently exercised. For example, a cooling performance, a lubricating performance and/or an operation pressure by the oil may decrease. Thus, it is important to adjust or control the amount of oil stored in the housing within a predetermined range.
According to JP2000-203293A (hereinafter referred to as Reference 2) and JP2005-201316A (hereinafter referred to as Reference 3) in addition to Reference 1, plural areas or portions for storing the oil are provided. An additional storage area besides a main storage area where the stator and the rotor are provided is formed to thereby control the amount of oil in the main storage area within the predetermined range.
In a case where the additional storage area as disclosed in References 1 to 3 is not provided, an oil discharge port may be formed at the housing at a predetermined height from an inner bottom portion of the housing. In such case, an operator puts the oil from an oil inlet port formed at the housing and determines that the desired amount of oil is stored in the housing when the oil is discharged from the oil discharge port. However, depending on positions of the oil inlet port and the oil discharge port, the oil may be discharged from the oil discharge port even when the desired amount of oil is not stored in the housing.
A need thus exists for a rotary electrical apparatus which is not susceptible to the drawback mentioned above.